feat(ci): separate macOS arm64 and x64 builds with individual code signing

Changes:
- Split macOS build into two separate jobs: build-macos-arm64 and build-macos-x64
- ARM64 builds on macos-14 (M1 runner) for native Apple Silicon builds
- x64 builds on macos-13 (Intel runner) for native Intel builds
- Each build has its own code signing and notarization process
- Artifacts renamed with -arm64 and -x64 suffixes for clarity
- Separate release jobs for each architecture
- Updated package.json mac targets from "universal" to ["arm64", "x64"]

This fixes code signing issues when building universal binaries and allows
faster parallel builds for each architecture.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -121,13 +121,15 @@
         {
           "target": "dmg",
           "arch": [
-            "universal"
+            "arm64",
+            "x64"
           ]
         },
         {
           "target": "zip",
           "arch": [
-            "universal"
+            "arm64",
+            "x64"
           ]
         }
       ],